vi PREFACE 



space for some of its fragments. In order that the whole might 

 be presented in sequential form it was therefore necessary to write 

 a book. 



I am greatly indebted to DORIS WULFF for her attention to 

 the manuscript; to JOSEPH B. HOMAN for his pen and ink draw- 

 ings; to JOSEF KUPKA for his photographs and tireless devotion 

 to the business of the day. 



MARTIN H. FISCHER. 

 EICHBERO LABORATORY OF PHYSIOLOGY, 

 UNIVERSITY OP CINCINNATI, 

 November 24, 1920. 



